[
https://issues.apache.org/jira/browse/KAFKA-15372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17755997#comment-17755997
]
Daniel Urban commented on KAFKA-15372:
--------------------------------------
[~gharris1727] I have a bit more information: we managed to deterministically
reproduce the issue if we use a 2 instance cluster, and make a change in the
config, then wait a long time between the instance restarts. In our specific
test we wait 3 minutes after stopping the first MM2 instance, then wait 3
minutes after starting the first MM2 instance, then wait 3 minutes after
stopping the second MM2 instance, and so on.
At the end of this process, the config change does not get applied.
I think this all depends on the rebalance - if the rebalance finishes before
the MM2 instance bounces back, the leadership will always move to the other
node.
> MM2 rolling restart can drop configuration changes silently
> -----------------------------------------------------------
>
> Key: KAFKA-15372
> URL: https://issues.apache.org/jira/browse/KAFKA-15372
> Project: Kafka
> Issue Type: Improvement
> Components: mirrormaker
> Reporter: Daniel Urban
> Priority: Major
>
> When MM2 is restarted, it tries to update the Connector configuration in all
> flows. This is a one-time trial, and fails if the Connect worker is not the
> leader of the group.
> In a distributed setup and with a rolling restart, it is possible that for a
> specific flow, the Connect worker of the just restarted MM2 instance is not
> the leader, meaning that Connector configurations can get dropped.
> For example, assuming 2 MM2 instances, and one flow A->B:
> # MM2 instance 1 is restarted, the worker inside MM2 instance 2 becomes the
> leader of A->B Connect group.
> # MM2 instance 1 tries to update the Connector configurations, but fails
> (instance 2 has the leader, not instance 1)
> # MM2 instance 2 is restarted, leadership moves to worker in MM2 instance 1
> # MM2 instance 2 tries to update the Connector configurations, but fails
> At this point, the configuration changes before the restart are never
> applied. Many times, this can also happen silently, without any indication.
--
This message was sent by Atlassian Jira
(v8.20.10#820010)
